High frequency switching is an important aspect of switching power supplies. High frequency switching can greatly reduce the size and weight of switching converter, and also improve converter power density. In order to realize high frequency operation, switching losses should be reduced. Soft switching technology is one method of reducing such switching losses. In soft switching, voltage or current of a switch in a switching converter can change according to sinusoidal or quasi-sinusoidal properties through principles of resonance. For example, when a voltage crosses zero, the switching device may be turned on, and when current crosses zero, the switching device may be turned off.